Due to the intractability of the problem, we propose the Particle Swarm Optimization (PSO) [1]}, [2]} to find an efficient 3D placement of the UAV, when the locations of indoor users are uniformly distributed in each floor. In [3]}, we prove that \(z_{UAV}\) =\(0.5z_{b}\)  and \(y_{UAV}\) =\(0.5y_{b}\)  when the locations of indoor users are symmetric across the dimensions of each floor. Then, we use the gradient descent algorithm to find \(x_{UAV}\)  that minimizes the transmit power required to cover the building.
